package ifo;

import java.util.*;
import java.io.*;

/**
 * Recursive file listing under a specified directory.
 * 
 * @author javapractices.com
 * @author Alex Wong
 * @author anonymous user
 */
public final class FileListing {

	/**
	 * Recursively walk a directory tree and return a List of all Files found;
	 * the List is sorted using File.compareTo().
	 * 
	 * @param aStartingDir
	 *            is a valid directory, which can be read.
	 */
	static public List<File> getFileListing(File aStartingDir)
	throws FileNotFoundException {
		if (aStartingDir.isFile()) {
			List<File> result = new ArrayList<File>();
			result.add(aStartingDir);
			return result;
		}
		validateDirectory(aStartingDir);
		List<File> result = getFileListingNoSort(aStartingDir);
		Collections.sort(result);
		return result;
	}

	// PRIVATE //
	static private List<File> getFileListingNoSort(File aStartingDir)
	throws FileNotFoundException {
		List<File> result = new ArrayList<File>();
		File[] filesAndDirs = aStartingDir.listFiles();
		List<File> filesDirs = Arrays.asList(filesAndDirs);
		for (File file : filesDirs) {
			if (file.getAbsolutePath().contains(".xls"))
				result.add(file);
			if (!file.isFile()) {
				// must be a directory
				// recursive call!
				List<File> deeperList = getFileListingNoSort(file);
				result.addAll(deeperList);
			}
		}
		return result;
	}

	/**
	 * Directory is valid if it exists, does not represent a file, and can be
	 * read.
	 */
	static private void validateDirectory(File aDirectory)
	throws FileNotFoundException {
		if (aDirectory == null) {
			throw new IllegalArgumentException("Directory should not be null.");
		}
		if (!aDirectory.exists()) {
			throw new FileNotFoundException("Directory does not exist: "
					+ aDirectory);
		}
		if (!aDirectory.isDirectory()) {
			throw new IllegalArgumentException("Is not a directory: "
					+ aDirectory);
		}
		if (!aDirectory.canRead()) {
			throw new IllegalArgumentException("Directory cannot be read: "
					+ aDirectory);
		}
	}
}
